1. Field of the Invention
The present invention relates to a method for estimating an amount of angular disagreement of planes of polarization between two polarization-maintaining optical fibers when connecting the polarization-maintaining optical fibers and relates to a method for connecting two polarization-maintaining optical fibers while controlling the angular disagreement using this method for estimating the amount of angular disagreement.
2. Description of the Related Art
Conventionally, there are two methods for measuring an amount of angular disagreement of planes of polarization between two polarization-maintaining optical fibers when connecting the polarization-maintaining optical fibers.
In the first method, polarized light which is emitted from a polarizer is passed through the polarization-maintaining optical fibers to be connected and received by an analyzer, and the amount of angular disagreement of the planes of polarization between the polarization-maintaining optical fibers is measured from the angular variation of the light which was received by an analyzer.
In the second method, the polarization-maintaining optical fibers is irradiated by light from the lateral side thereof, and the amount of angular disagreement of the planes of polarization between two polarization-maintaining optical fibers is measured by comparing images produced by the light which has been transmitted through the polarization-maintaining optical fibers. This method using a technique for adjusting axes of polarization of two polarization-maintaining optical fibers which are to be connected by an image processing and is used in an optical fiber fusion splicer, and a method for measuring the amount of angular disagreement of planes of polarization between two polarization-maintaining optical fibers using this technique is disclosed in Japanese Unexamined Patent Application, First Publication No. 8-114720.
However, in a method in which the polarizer and analyzer are used and the amount of angular disagreement of the planes of polarization between the polarization-maintaining optical fibers is measured by passing the light through the optical fibers, the set up of the polarizer and analyzer takes time, and as a result, it takes a lot of time to measure the amount of angular disagreement of the planes of polarization. In addition, after the installation of the connected polarization-maintaining optical fibers in a device and the like, there are cases in which the light cannot be passed through the polarization-maintaining optical fibers, and as a result, the amount of angular disagreement of the planes of polarization cannot be measured.
Furthermore, in a method in which irradiating the light on the polarization-maintaining optical fibers from the lateral side and measuring the amount of angular disagreement of the planes of polarization between the polarization-maintaining optical fibers from the images of the transmitted light, angles of the planes of polarization between two polarization-maintaining optical fibers can be adjusted; however, it is not easy to determine the amount of angular disagreement of the planes of polarization. In addition, in the method disclosed in Japanese Unexamined Patent Application, First Publication No. 8-114720, the amount of angular disagreement of the planes of polarization is measured by comparing numerical values obtained from a position of each peak of the transmitted light; however, the relationship between the position of the peak and the amount of angular disagreement of the planes of polarization varies in accordance with the characteristics of the polarization-maintaining optical fibers, especially with the shape, material, and refractive index of stress applying sections provided therein, and therefore, the amount of angular disagreement of the planes of polarization cannot be accurately measured from the position of the peak.